AD7856ARS datasheet(27/32 Pages) AD

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AD7856

–27–

REV. A

Interface Mode 2 Configuration

Figure 35 shows the flowchart for configuring the part in Inter-

face Mode 2. In this case the read and write operations take

place simultaneously via the serial port. Writing all 0s ensures

APPLY

SYNC (IF REQUIRED), SCLK, WRITE

TO CONTROL REGISTER SETTING NEXT

CHANNEL, CONVST BIT TO 1, READ

PREVIOUS CONVERSION RESULT ON

DOUT PIN (NOTE 1)

INITIATE

CONVERSION

SOFTWARE

START

POWER-ON, APPLY CLKIN SIGNAL,

WAIT 150ms FOR AUTOMATIC CALIBRATION

PULSE

CONVST PIN

WAIT FOR BUSY SIGNAL TO GO LOW

WAIT FOR BUSY BIT = 0

SERIAL

INTERFACE

MODE

YES

APPLY

SYNC (IF REQUIRED), SCLK, READ

CURRENT CONVERSION RESULT ON

DOUT PIN, AND WRITE CHANNEL SELECTION

NOTE 1: WHEN USING THE SOFTWARE CONVERSION START AND TRANSFERRING DATA

DURING CONVERSION, THE USER MUST ENSURE THAT THE CONTROL REGISTER WRITE

OPERATION EXTENDS BEYOND THE FALLING EDGE OF BUSY. THE FALLING EDGE OF

BUSY RESETS THE CONVST BIT TO 0 AND ONLY AFTER THIS TIME CAN IT BE

REPROGRAMMED TO 1 TO START THE NEXT CONVERSION.

WAIT APPROX 200ns AFTER

CONVST RISING EDGE

APPLY

SYNC (IF REQUIRED), SCLK, READ

PREVIOUS CONVERSION RESULT ON DOUT

PIN, AND WRITE CHANNEL SELECTION

TRANSFER

DATA DURING

CONVERSION

APPLY

SYNC (IF REQUIRED), SCLK, WRITE

TO CONTROL REGISTER SETTING NEXT

CHANNEL, CONVST BIT TO 1, READ

RESULT ON DOUT PIN FOR

CONVERSION JUST COMPLETED

WAIT FOR BUSY SIGNAL TO GO LOW

WAIT FOR BUSY BIT = 0

YES

TRANSFER

DATA DURING

CONVERSION

Figure 35. Flowchart for Setting Up, Reading and Writing in Interface Mode 2

that no valid data is written to any of the registers. When using

the software conversion start and transferring data during con-

version, Note 1 must be obeyed.

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